The invention relates to an electric switch, in particular for medium or high-voltage, the switch comprising a first arcing contact surrounded by a puffer break chamber in which gas is pressurized by the thermal effect, and a second arcing contact movable in an axial direction relative to the first contact. The break chamber has an internal partition separating a first compartment of fixed volume from a second compartment of smaller volume, both compartments being filled with said gas under pressure and each possessing an orifice for blasting the arc. The orifices are separate and disposed in series along said axial direction, and the second arcing contact is arranged initially to release the orifice of the first compartment while still closing the orifice of the second compartment during separation of the two contacts.
The object of the invention is to propose such a switch which, by puffer action, is capable of breaking short-circuit currents that are low (i.e. currents of up to 30% of the break power of the switch), and also currents that are high, while using drive energy that is as small as possible.
To this end, the invention provides such as switch, wherein each compartment is connected to its own orifice via a respective blast channel, wherein the first compartment with its blast channel and its orifice are placed adjacent to said first arcing contact, wherein the second compartment is placed mainly between the ends of the first arcing contact and a permanent-current contact corresponding thereto, and wherein the compartments communicate with each other via a channel that is closed by an excess pressure vent device allowing gas at excess pressure to pass in one direction only from the smaller volume compartment to the larger volume compartment.
The larger-volume compartment is optimized to break higher currents, i.e. currents greater than 30% of the break power of the switch. The smaller-volume compartment is optimized to break smaller currents. With this disposition having two thermal volumes, the switch can break currents over the entire break range of the switch by puffer means.
In a particular embodiment of the puffer switch of the invention, the switch has a nozzle of insulating material placed coaxially around the first contact with the second arcing contact penetrating therein, at least the second of the two compartments being placed inside said nozzle, the inner partition which separates the two compartments being formed by a portion of the nozzle. In a variant of this particular embodiment, the blast channel of the first compartment is separated from the first arcing contact by a wall surrounding said contact and made of the same insulating material as the nozzle. Spacers can be placed in the blast channel of the second compartment and secured to the inner partition which separates the two compartments and also to the main body of the nozzle. In an additional variant, a permanent magnet producing a turning magnetic field for interrupting the electric arc is placed inside the nozzle or indeed inside the second arcing contact.